Although it can be applied to any objects to be assembled, the present invention and the problems on which it is based are explained in more detail with reference to an approximately cylindrical section of a fuselage of an airplane.
Usually, fuselage shells for airplanes are produced in what is known as a lightweight construction from an outer skin which is reinforced on the inner side by a two-dimensional structure of stringers extending in the longitudinal direction of the airplane and frames extending transversely to the longitudinal direction of the airplane. The production process thereby involves the separate assembly of individual fuselage sections, which have for example approximately the form of a lateral surface of a cylinder or a truncated cone, to be subsequently joined together to form a complete airplane fuselage.
The company Vought Aircraft shows on its website http://www.voughtaircraft.com/gallery/locations/locations.htm an apparatus in which the outer skin of an airplane fuselage section is suspended between two rotatably mounted rings before nondestructive inspection of the outer skin.
In the assembly of such fuselage sections, conventionally the outer skin of the section concerned is placed in a rigid jig formed in a way corresponding to the form of a section and is equipped by fitters with frames, clips for fastening the frames, holders for cabling running in the airplane, reinforcing trusses in the floor and ceiling areas, window frames and other assembly parts. The rigid form of the jig prevents the outer skin, which at first is not yet equipped with frames, from being deformed under the effect of gravitational force, keeps the outer skin in the desired final form of the section during the assembly work and in this way makes it possible for the frames to be precisely fitted.
In the case of conventional jigs, working platforms and frameworks of various heights on which the fitters move about are used inside and around the section to be assembled. Apart from the expenditure on such platforms, there is the problem that the fitters have to carry out much of their work in an ergonomically unfavorable position. For example, in the assembly of a truss in the floor region of the section, a fitter has to carry out work below his own feet, and in the ceiling region he has to carry out work above his own head. Furthermore, the frameworks and working platforms take up space, which restricts the amount of work that can be carried out simultaneously inside the section and leads to an increased space requirement of the overall jig outside the section.
While in the case of a traditional aluminum construction, the outer skin of the section can be put together from a number of portions which have already been provided at least partially with frame portions or certain assembly parts before installation, when the outer skin is produced from carbon fiber reinforced plastic the outer skin of the section is produced in one piece, by laminating carbon fibers wound around the entire circumference of the section. For this reason, the extent of work to be carried out by fitters on the jig increases, and consequently the significance of the problems described increases.